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RENESAS TOOL NEWS on April 1, 2005: RSO-M3T-NC308WA-050401D
A Note on Using
the M3T-NC308WA C-Compiler Package
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Please take note of the following problem in using the M3T-NC308WA C-compiler package with an assembler and an integrated development environment.
This C-compiler package is used for the M32C/90, M32C/80, and M16C/80series of MCUs:
- On using if-else constructs
- Versions Concerned
M3T-NC308WA V.5.00 Release 1 through V.5.20 Release 02,
which are used for the M32C/90, M32C/80, and M16C/80 series of MCUs.
- Description
Regardless of whether the result of evaluation of the controlling expression in an if statement is TRUE or FALSE,
incorrect code will be generated if statements for assigning a constant to a member of a bit field exist in the TRUE and FALSE statements.
- 2.1 Conditions
-
This problem occurs if the following conditions are all satisfied:
| (1) |
An if-else construct exists. |
| (2) |
Regardless of whether the result of evaluation of the controlling expression in an if statement in (1) is TRUE or FALSE,
constants are assigned to members of bit fields of a structure, where the bit fields have the same name as variables. |
| (3) |
The bit fields to which constants are assigned in (2) are1 bit wide (those not assigned can be wider than 1). |
| (4) |
The bit fields in (2) are different in bit positions depending on whether each of them is put in the TRUE or FALSE statement. |
| (5) |
The constants in (2) are also different depending on whether each of them is assigned in the TRUE or FALSE statement. |
- 2.2 Example
-------------------------------------------------------------
char c;
struct S
{
int b0:1; /* Conditions (3) and (4) */
int b1:1; /* Conditions (3) and (4) */
int b2:1;
int b3:1;
int b4:1;
int b5:1;
int b6:1;
int b7:1;
int b8:8;
}s;
void func( void )
{
if ( c == 1 ){ /* Condition (1) */
s.b0 = 0; /* Conditions (2), (3), (4), and (5) */
}
else{ /* Condition (1) */
s.b1 = 1; /* Conditions (2), (3), (4), and (5) */
}
}
-------------------------------------------------------------
- Workaround
Place a dummy asm() function anywhere in the else block.
-------------------------------------------------------------
char c;
struct S
{
int b0:1;
int b1:1;
int b2:1;
int b3:1;
int b4:1;
int b5:1;
int b6:1;
int b7:1;
int b8:8;
}s;
void func( void )
{
if ( c == 1 ){
s.b0 = 0;
}
else{
s.b1 = 1;
asm(); /* Dummy asm() function placed */
}
}
-------------------------------------------------------------
- Schedule of Fixing the problem
We plan to fix this problem in the next release of the product.
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